docs: def get_centrals(self):
          """Get the central wavenumbers or central wavelengths of all channels,
          depending on the given 'wavespace'
          """
          result = {}
          for chname in self.rsr.keys():
              result[chname] = {}
              if self.wavespace == "wavelength":
                  x__ = self.rsr[chname]["wavelength"]
              else:
                  x__ = self.rsr[chname]["wavenumber"]
              for sat in self.rsr[chname].keys():
                  if sat in ["wavelength", "wavenumber"]:
                      continue
                  if type(self.rsr[chname][sat]) is dict:
                      result[chname][sat] = {}
                      for name in self.rsr[chname][sat].keys():
                          resp = self.rsr[chname][sat][name]
                          result[chname][sat][name] = get_central_wave(x__, resp)
                  else:
                      resp = self.rsr[chname][sat]
                      result[chname][sat] = get_central_wave(x__, resp)
  
          if self.wavespace == "wavelength":
              self.central_wavelength = result
          else:
              self.central_wavenumber = result